Drill grinder



Feb. 22, 1938. Q ADAMS 2,109,308

DRILL GRINDER Filed March 3, 1936 6 Sheets-Sheet 1 n u ll l INVENTOR,

Car/all E fiat/l5,

ATTORNEY.

C. E. ADAMS DR ILL GRINDER Feb. 22, 1938.

Filed March 5, 1936 6 Sheets-Sheet 3 INVENTOR, $270211. 14 m,

ATTORNEY.

Feb. 22, 1938. c, ADAMS 2,109,308

DRILL GRINDER Filed March 3, 1936 6 Sheets-Sheet 4 INVENTOR, 55 Wlm 670/17 w @ow-w/ ATTORNEY.

Feb. 22, 1938. c, ADAMS 2,109,308

DRILL GRINDER Filed March 5, 1936 6 Sheets-Sheet 5 [I INVENTOR,

WWI/by 0465mm ATTORNEY.

Feb. 22, 1938. c s' 2,109,308

DRILL GRINDER Filed March 3, 1956 6 Sheets-Sheet 6 INVENTOR, wzmll Z7 2702mm,

07 'Arronm zi Patented Feb. 22, less 2,109,308

UNITED STATES PATENT OFFICE mum. oamnlin Carroll E. Adams, Pawtucket, n. 1.

Application March 3, 1938, Serial No. cases 9 Claims. (01. 51-219) This invention relates to improvements in face surface of the wheel at exactly the correct drill grinders. angle to the work to be ground.

An object or this invention is to provide, in a These, and other objects and advantages of drill grinder, means for grinding all of the lips this invention, will be more completely disclosed or faces of the drill point at a single setting of and described in the following specification, the 6 the drill. It is customary, in drill glnders now accompanying drawings, and the amended used in the art, to grind one lip of the drill, then, claims.

remove the drill from its holding means, turn Broadly, the invention comprises a base, a it, (as 180 degrees for a drill having two lips), grinding unit including grinding wheels and moand relocate it in the holding means for grindtor mounted on the base, a feed table slidably l0 ing the next, or second lip. This operation tends supported on the base, a drill holder. means for to inaccuracy in setting of the drill, resulting locating a drill in the holder in a definite relain unequally ground drill faces. By completely tion thereto, a bearing for the holder pivotally grinding all of the faces of the drill point at one secured on the table, adjustable stop means on setting, an absolutely symmetrical drill point, the feed table, a cam on the drill holder engaged 15 having each lip identical in all its phases, is by the stop means for moving the bearing and mandatory. holder about the pivot 01' the bearing, co-operat- A second object of the invention is to provide, in: means between the holder and the bearing in a drill grinding device, means for grinding for moving the holder longitudinally oi! its axis,

identical relief angles and for all diameters of so-Op means between the bearing a drills. the table for locating the bearing at predeter- A third object of this invention is to provide, mined positions on the table, adjustable means in a drill grinding device, means for grinding a for holding the drill in proper relation to a grindchamiered face .or surface interposed between ing wheel for grinding or thinning the web of a the lip face and the land face of the drill, the the drill, and means for moving the table toward chamfered face being ground to the some relief and away from a grinding wheel.

angle, or spiral, as the lip face. Drills, having a A preferred embodiment of this invention is straight lip face, characterized by a straight line illustrated in the accompanying drawings, in

extending from the point of the drill to the which:-

land, wear most rapidly at the intersection of Fig. 1 is a plan view of the gri machine- 30 the lip face with the land. By chamfering this Fig. 2 is a front, elevational view of the same. intersection, thus interposing a secondary lip Fig. 3 is a longitudinal, sectional view of the face between the primary lip face and the land, d ill holde 0 q the intersecting angles of the faces and the sec- 4 is a Blew-$101181 View of the fill-ms mountondary face and the land is materially increased, e6 0!! h q 35 and ,the useful life of the drill is materially F a. 5 is a de e p d v w of one-half of the lengthened. thrust cam.

A further object of this invention is to provide, 6 is Parflalsectional View through the in a drill-grinding device, means for thinning thrust taken on the M of m the web of the drill and grinding the correct 7 is View similar to taken on e h line 1-1 of Fig. 4 of the thrust cam. fiifi g gfi'fififig the web the Fig. 8 is a side,'elevational view of the drill i still further object of this invention is to f fs f zfi g ff f g igfi m provide, in a drill-grinding device incorporating pomg'locater the above described features, sufilcient adjustamg m is partial sideelevatlongl vi w f bility in the various controlling elements to perthe Q-m point flm t -atmg the method of nut as wide a range as is practical in the choice forming t same, 7 of point angle and other characteristics of the Fig. 11 is an end view of the drill point locatcr. 5U drill p so that the d i ind r may be ad- Fig. 12 is a side, elevational view of the drill so justed to grind drill points for any and all conpoint locater, as it is positioned in the drill loditions and customs. cater.

Another object 01 this invention is to provide Fig. 13 is a graphical illustration of the relameans, in a drill-grinding device, for controlling tion of the drill point and cutting angle to the u the dressing of the grinding wheel to resent the drill diameter. an

Fig. 14 is a side view, partially in section, illustrating the method of co-relating the drill diameter and location of the drill point locater.

Fig. 15 is a side, elevational view of the quill bearing and stop device.

Fig. 16 is an end, elevational view of the same.

Fig. 17 is a partial, sectional view of the quill bearing.

Fig. 18 is a partial, sectional view on the line lB-IB of Fig. 17.

Fig. 19 is a partial, sectional view, taken on the line l8-i8 of Fig. 18.

Fig. 20 is a partial, plan view, showing the bearing, stop, and quill in position for grinding the drill point.

Fig. 21 is a view similar to Fig. 20, showing the various parts in position for grinding the secondary faces on the drill point.

Fig. 22 is a plan, or end view, of a typical drill point.

Fig. 23 is a side, elevatlonal view of a typical drill point.

Fig. 24 is a side view of a drill point, before grinding the secondary faces.

Fig. 25 is a side view of the same drill point, after grinding the secondary faces.

Fig. 26 is a view similar to Fig. 20, showing the bearing in position for dressing the grinding wheel.

Fig. 27 is a partial, sectional view on the line 2l--21 of Fig. 26.

Fig. 28 is a side, elevational view of the drill support for thinning the web of the drill, and

Fig. 29 is a front, elevational View of the same.

Referring now to the drawings in detail, in which like numerals refer to like parts throughout:

A base member I has secured thereon'a motor 2, having a shaft 3 on which is secured, in the usual manner, grinding wheels 4 and 5. Guards and i are supported over the wheels 4 and 5, respectively, on posts 8 and 9. which are secured in the base I. A plate i0, secured on the base I, slidably supports a feed table II, and this table may be moved toward and away from the axis of the grinding wheel 4, on the plate N, by means of a screw and handwheel l2. A quill holder bearing and stop device are pivotally secured on the table H, and a drill-locating device is secured on the base i. These devices will be described in detail later, in order of their use. A drill holder, or quill H, (see Fig. 3), is provided in cooperation with the grinding machine, and is illustrated in detail in Figs. 3 to '7, inclusive. A sleeve member I! is provided with a bore l4 terminating at one end in a threaded portion (5 and at the opposite end in a tapered portion IS. A drill chuck l 8 may be secured in the sleeve I3 between the inclined end l6 and a forcing sleeve l 9, which is slidably supported in the bore I4 and actuated by means of a screw 20, engaged in the threaded portion IE or the sleeve l8. Variable sizes of drill chucks may be used in the sleeve l3 by varying the inside diameter of an adapter sleeve 2|, inserted in the bore l4 between the drill chuck I8 and sleeve member II. The chuck I8 is formed with opposed, enlarged, tapering end sections 22 and a plurality oi slots 22, which extend alternately from opposite faces of the sections 22. The slots 23 provide spring portions in the chuck l8 for grippin and releasing a drill 24. One of the tapered end portions 22 is located in the adapter sleeve 21 and the opposite tapered end portion is located in the end of the forcing sleeve I8. Rotation of the screw 20 into the sleeve II will advance the forcing sleeve l9 onto one of the inclined portions 22 of the chuck II, thereby contracting the chuck III by engagement of the inclined, or tapered surfaces, causing the chuck to grip the drill 24 with an equal force at each of the ends 22. Reversal of the movement or the screw 20 will release the pressure on the chuck l8 and permit the same to expand, thereby releasing the drill 24.

Two cams are secured on the sleeve member l3; a "throw cam 25 by the key l3, for moving the drill point in a circular, or angular movement, about the pivot point 56 on the feed table II, and a thrust" cam 26 having a press fit in the cam 25 for moving the drill point longitudinally of its axis. These cams bear a definite relation to each other and to the drill point, and move as a unit, being secured together by dowels 21. The circular or angular throw cam 25 for the drill is provided with operating lobes or flanges 28, having advance cam surfaces 25 and return cam surfaces 30, with a dwell surface 3| between them. The thrust cam 26 is provided with a circumferential cam flange 32, having an inner edge 33 which lies in the same plane throughout its circumference, as shown in Figs. 3, 5, 6, and 7, and an outer edge 34 which advances radially outward from a point 35 in the same plane with the inner edge I3 to a peak point 36, thence in a sharp return to the point 35. This construction results in a cam surface 31 which progresses in pitch from a level at 35 to its extreme pitch at 36, as indicated in the developed view in Fig 5. Each of the cams 25 and 26 is provided with a number of cam surfaces equal to the number of lips on the drill to be ground. The purpose and operation of these cams will be explained later.

As the throw cam 25 and thrust cam 26 control, as a unit, the shape and grinding of the drill point, and must bear a definite relation thereto, a drill locator 38, (see Fig. 8), is provided and secured on the base I, (see Fig. 1), for locating, or positioning, the drill point in the quill, or drill holder H. The member 38 is formed with a bearing sleeve 39 in which the quill H may be slidably supported, and a drill point locating arm 4|! spaced from the sleeve 39. A collar ll, provided with gauge or graduation marks 2, which co-operates with an index mark 43' on the sleeve 39, (see Fig. 8), is rotatably supported in the sleeve 39, as shown in Fig. 1, and is provided with a pin or stud H which reg isters with an opening 45 in line with the point 35, in the thrust cam 26, for definitely locating the cams 2| and 2l, circumferentially, relative to a drill point locator l6, shown in Figs. 9, 10, 11, 12 and 14, which is slidably guided in the standard or arm II. The drill point locator member 46 is prevented from rotary movement in the arm Ill by a pin 41 on a jaw l8, having a tapered face 45 opposed to a fixed jaw 50 on the arm ll. The member l6, carrying the tapered face jaw 48 is slidably secured in the arm 40, and may be clamped in position, when set for a certain diameter 0! drill by means of a set screw ii.

In order to grind drill points with identical relief angles and synonymous relief surfaces, it has been necessary to provide means for setting the drill point, in relation to the pivot point of the angular or throw cam 25, so that each of the distances A, (see Fig. 13) is a definite proportion of the corresponding diameters B of the drill to be ground. with each of the points C over the pivot point 58 for the cam 25. The distance, therefore, of the drill point D from the cam 25 will vary directly in proportion to the diameter of the drill. This distance is determined by laying the drill to be ground between the surface 49 of the jaw 45 and the Jaw 50, as indicated in Fig. 14. This operation locates the end 52 of the drill point locator 45 with relation to the throw cam 25, and thrust cam 25. The cutting edge 24' of the drill 24 is located, circumferentially, in proper relation to the earns 25 and 25. by engagement against a plane, or straight surface 55. cut in the end of the locator 45. To set a drill properly in the quill sleeve II, the drill is first placed between the laws 45 and 55 to locate the point of the locator member 45, after which the set screw i may be tightened, and any number of drills having the same diameter will be identically located in the quill sleeve ll. After locating the point of the member 45, the drill is inserted in the chuck III, with suiiicient pressure exerted by the screw 20 to hold the drill lightly. The quill sleeve i3 is then inserted in the sleeve 39 of the locator 35 with the recessed surface 25' of the cam 25 abutting the graduated collar 4| and the pin 44, engaged in an opening 45 in the drill thrust cam 25. With the quill thus assembled in the locator 35, the drill is moved longitudinally and circumferentially, until the drill point impinges against the drill point locator 45 with the cutting edge 24' against the fiat plane surface 53, as indicated in Fig. 8. The screw 25 is then tightened to firmly hold the drill in the chuck l5.

With the drill 24 firmly held in the quill sleeve IS, in proper relation to the earns 25 and 25, the quill I3 is then removed from the locator 38 and slidably inserted in a bearing sleeve 54 on an arm 55 which is pivotally located on a stud 55, secured in the table H, (see Figs. l5, l6, and 1'7). The stud 55 is the pivot point previously referred to in this specification. A sleeve member 51, fixedly secured in the bearing sleeve 54 with the screw 54', is formed with a flanged portion 58, on which is secured a disc 59 by the screw 59', provided with a V-slot 55. A flanged disc, or cam member BI, is rotatably supported on the disc 59 and held in adjusted position by means of a nut 52, threadably secured on the sleeve 51. A pin, or stud 55, having a T head 54, which is slidably guided in the slot Bil, projects through a cam slot 65 formed in the member 5|. Rotation of the member 5| will move the stud radially, thus varying its distance ber 5| with an index mark 51 on the flange 55.

When the quill i3 is inserted in the sleeve 5'! and revolved by the part 25, engagement of the stud 55 on the cam surface 31 of the thrust cam 25 results in longitudinal movement of the quill i3, relative to the sleeve 51 and grinding wheel 4.

The amount of this movement is determined by the radial position of the stud 53 on thecam surface 51.

A second arm member '55 is also pivotally secured on the table II by the pivot stud 55, and is provided with an indicator finger portion 55, which corresponds with the normal position of the axis of the bearing member 54 and quill ll. This indicator finger 58 co-operates with an index dial III on the table H, (see Figs. 20 and 21), to control the normal axis of the quill l3 and thereby determine the included point angle which shall be ground on the drill point. A stop bar I i, secured in bosses 12 formed on the member 58, is engaged by the cam 25 and by this engagement moves the quill l5 through an arc, indicated at 12, in Fig. 20. as the quill I5 is revolved in the bearing 54. Thus, the angular relation of the axis of the quill 13 with the grinding wheel 4 is controlled by engagement of the cam 25 against the stop bar II, and the stop bar H is adjustably located according to the desired reading on the index In on the table II.

In operation, as the quill I5 is revolved within the sleeve 51, with the necessary forward pressure exerted against the rear of the quill, cooperation of the bar II and cam 25 with the stud 53 and cam 25, will present the drill point to the grinding wheel in the manner required to grind the point to the required characteristics, and with the predetermined relief angle and included point angle. As the cam 25 throws the axis of the quill II to its outermost travel, thereby oompleting the grinding of one lip of the drill, the quill i3 is held in this extreme position by the dwell surface 3| on the cam 25, while action of the pin 53 against the quick return surface 51' of the cam 25 will pull the drill point away from the grinding wheel to provide a clearance necessary to prevent grinding of the point of the drill while approaching the second lip, or cutting edge. As the second cutting edge is presented to the wheel, the co-operation of the cams 25 and 25 and their related parts again feed the quill forwardly and radially, grinding a second relief surface identically the same as the first. Thus, all the cutting lips of the drill point are ground at a single setting of the drill and without removing the quill it from the bearing sleeve 54.

After the relief surfaces 24 have been ground on the drill point as explained above, a secondary relief surface 24 may be ground on the drill point, to provide a chami'ered effect to the drill, as indicated in Fig. 25, in order to reduce wear on the drill point and prolong its useful life. This secondary surface 24-' is. ground with the quill and bearing 54 in a position similar to that indicated in Fig. 21. A boss 15, formed on the arm 55, is provided with a spring pin I6, (see Fig. 2'7), and the table II is provided with a plurallty of holes 11 having a common radius from the pivot 55, in any one of which the pin I5 may be engaged. A gauge I8, co-operating with an indicating ridge 19, formed on the boss 15, directs the proper hole in which to set the pin 15 for the angle desired. With the arm fixed in position by the pin 15, rotary or angular movement of the quill ll, co-operating with engagement of the cam 25 and pin 55, will grind a secondary relief surface 24 having exactly the same relief angle, or spiral, as the surface 24, as indicated in Fig. 25. Preferably, the angle of intersection of the two relief surfaces and the angle of intersection of the secondary relief surface and the surface of the land should be equal, as indicated at E in Fig. 25, but any angle may be formed by adjustment of the arm 55 by means of the pin 15. Also, the relative lengths F and G of the relief surfaces may be controlled and varied by the feed of the table II toward the, grinding wheel 4.

If the finished drill point is to correspond in its various characteristics to the settings provided on the feed table Ii, it is imperative that the plane of the face 4' of the grinding wheel 4 should be at right angles to the direction of feed of the table H.

The wheel I is dressed to produce this condition in the manner indicated in Fig. 26. A hole 89, in the feed table II, similar to the holes TI, is locateddirectly opposite the pivot point 56, so that when the bearing arm 55 is swung until the pin 16 is located in the hole 99, the axis of the bearing sleeve 5| will be at right angles to the feed of the table II. with the bearing sleeve 54 set in this position, a dressing tool 9! is slidably supported in a sleeve 82, which is removably supported in the sleeve 51, and the tool 9| may be moved back and forth across the grinding face of the grinding wheel, as the feed table II is fed toward the grinding wheel, until the wheel is properly dressed.

A device for grinding the inside of the lands of the drill for thinning the web, after the point of the drill has been completed on the wheel 4, is illustrated in Figs. 1, 2, 28 and 29. A supporting arm 83 is pivotally supported on a stud Bl secured in the base i, and may be secured in an adjusted position on the stud 94 by means of a clamping bolt 85. The outer end of the arm 93 is provided with a hub 86, having an upwardly extending stop boss 81. A shaft 99 is fixedly secured in the hub 96, and is threaded at its outer end 89 for receiving an adjusting nut 99. A drill rest 9| is revolvably supported on the shaft 88 and held against the nut 99, in spaced relation with the hub I6, by-a compression spring 92. The drill rest 9| is formed with a bed portion 98, provided with a v-shaped groove 94 for receiving a drill 2i, and the bed 93 and groove 94 are set at an angle to the grinding wheel 5 which, when the drill is ground on the wheel' I, will form the proper front rake for the cutting edge of the drill. A limit, or stop screw 95, is threadably secured in a boss 99 extending outwardly from the side of the bed 99, and provides means for limiting the movement of the drill rest 9i around the shaft I9, thereby limiting the movement of the point II of the drill 24 toward the wheel 5. A foot, or stop member 91, adiustably secured on a rod 98 projecting from the bed 93, provides a support for the end of the drill 24, and may be set to accommodate any desired length of the drill. The depth of the cut, from the perimeter of the drill toward its axis, is controlled by cooperation of the boss 91 and limit screw 96, and the length of the cut, longitudinally of the axis of the drill, is determined by adjustment of the arm 91 on the pivot stud 8|. Lateral movement of the bed 9|, to present the drill point in proper relation to the wheel, is governed by co-operation of the take-up nut 99 and spring 92. Once set, this device will grind a front rake and thin each side of the web of a drill point exactly alike, and will produce identical characteristics on each lip of all drills having the same diameter and length.

The machine may be adjusted to grind any desired point angle and any desired relief angle on a drill point, and when once set, or adjusted, will grind each lip of every drill having the same diameter with identical characteristics, in all respects. It will be readily understood by those skilled in the art, that, whereas, the drawings illustrate the various elements of the grinding machine, as adapted for the common type of drill having two lips. drills having from one to any number of lips may be ground, simply by making the throw and thrust cams with a number of operating surfaces corresponding to the number of lips on the drills to be ground. Also, by reversing the circumferential movement of the quill and the circumferential arrangement of the operating surfaces of the throw and thrust cams, and revolving the drill point locator through 90 degrees, so that the plane or straight surface 53' is vertical. lefthand drills may be ground on the same machine.

What I claim is:-

1. In combination, in a drill grinding apparatus, a base, a grinding wheel mounted on the base, means for operating the grinding wheel, a clutch for holding a drill, a bearing sleeve in which said clutch is slidably and rotatably supported, means for moving said clutch longitudinally in said bearing sleeve when said clutch is rotated comprising a radially adjustable stud on said bearing sleeve and a cam on said clutch cooperating with said stud, said cam being provided with a plurality of arcuate cam faces, each of said cam faces having an inner annular edge in a plane perpendicular to the axis of said clutch and an outer annular edge in a plane at an angle to the plane of the inner edge, as described.

2. In combination, in a drill grinding apparatus, a base, a grinding element thereon, means for operating said grinding element, a clutch for holding a drill, a bearing pivotally secured on said base in which said clutch is slidably and rotatably supported, means for adjustably controlling longitudinal movement of said clutch comprising a cam secured on said clutch and provided with radially warped cam faces and a radially adjustable stud on said bearing engaged by said cam faces, and means for imparting an intermittent oscillatory movement to said bearing comprising a second cam secured on said clutch and provided with advance and return surfaces spaced by a dwellsurface and a bar engaged by said last-named cam surfaces, said bar being pivotal ly and adjustably secured on said base.

3. In a drill grinding device, a base, a plate movable thereon, a sleeve, means for retaining a drill to be ground in said sleeve, two cam members secured on said sleeve, a bearing pivotally secured on said plate in which said sleeve may be slidably and rotatably supported, a grinding element, adjustable means for engaging one of said cam members for controlling oscillatory movement of said bearing on its pivot, adjustable means engaging the other of sa d cam members for controlling longitudinal movement of said sleeve in said bearing, and cooperating elements on said cams for holding said bearing stationary while said sleeve is moved longitudinally away from said grinding element.

4. In a drill grinding device, a base, a grinding element, a plate part movable on said base in a direction perpendicular to the face of said grinding element, a sleeve member, means for retaining a drill to be ground in the sleeve member, two cam members secured on the sleeve member and to each other, a pivoted bearing sleeve in which the drill-retaining sleeve is located, one of the cam members operating to move the drill axially towards the grinding element an adjustable buttress on said plate the other cam member simultaneously operating in cooperation with said buttress to oscillate the drill about the pivot point of the bearing for imparting relief surfaces to the lips of the drill, and means for positioning said bearing sleeve on said plate for grinding secondary or chamfered spiral faces between the face]: of the ground lips and the faces of the lan 5. In a drill grinding device, a base member,

a plate part movable thereon. a sleeve member. means for retaining a drill to be ground in the sleeve member. two cam members secured to the sleeve member and to each other, a pivoted bearing sleeve in which the drill-retaining sleeve is located, a grinding element, a stud on said sleeve member cooperating with one oi the cam members to move the drill axially towards the grinding element, an adjustable buttress pivoted on the same axis with said bearing sleeve and cooperating with the other cam member to simultaneously oscillate the drill about the pivot point of the bearing for imparting relief suriaces to the lips of the drill, means for latching the sleevebearing member to the plate part on the base, in any one o! a plurality oi positions for varying the chamfered angle of the drill being ground.

6. In a drill grinding apparatus, a base. a grinding wheel, means for operating said wheel, a pivot on said base, an arm connected to said pivot, a bearing sleeve on said arm, a drill holder slidably and rotatably supported in said bearing sleeve. a bar connected to said pivot, means for adjustably positioning said bar, a cam on said drill holder having cam lobes engageable on said bar. a stud on said bearing sleeve, a second cam on said drill holder having cam laces engageable on said stud, means for freeing a drill in said drill holder from said grinding wheel after one lip oi the drill has been ground and before the next lip is ground comprising quick return faces on said second cam cooperating with dwell surfaces on said first-named cam. whereby said bearing sleeve is held stationary while said drill holder is moved longitudinally away from said grinding wheel. as described. I

I. In a drill grinding apparatus, a base, a grinding wheel mounted on said base, a table slidably secured on said base for movement in a direction perpendicular to the face 0! said grinding wheel a bearing sleeve pivotally secured on said table, said table being provided with-a plurality ct openings. latch means on said bearing sleeve cooperating with said openings for adiustably positioning the axis of said bearing sleeve relative to the face of said grinding wheel, one of said openings cooperating with said latch means to position the axm of said bearing parallel to the lace oi said grinding wheel.

8. In combination. in a drill-grinding machine,

a grinding wheel, a table member having gradu ation marks thereon, an arm member pivotally connected to the table member and having an indicating finger portion which co-operates with the graduation marks on the table member, a quill holder for the drill, the axis of which corresponds with the indicating linger, a stop bar pivotally connected on said table member, a

cam member carried by the drill holder engaging the stop bar when the drill holder is rotated for moving the pivotally connected arm, and means for automatically advancing the drill towards the grinding wheel when the drill holder is retated. whereby the drill point is ground with a. predetermined reliei' angle and included point angle, as described.

9. In a drill-grinding machine, a grinding wheel, a fixed table member, having index gradnations therein, an arm member pivotally connected to the table, a bearing sleeve on the arm, a second sleeve secured to the bearing sleeve and formed with a flange portion, a disc secured to the ilange portion and having a slot therein, a member having a cam slot rotatably supported on the disc, means for adjustably securing the rotatable member with a cam slot to the disc, a pin slidably guided in the slot oi the disc and located in the cam slot of the rotatable disc, a drill holder rotatably supported in the second sleeve of the bearing sleeve, index means on the rotatable member having the cam slot for indicating the radial position of the pin relative to the axis of the bearing and second sleeve, a holder for, the drill, two cam members secured to the drill holder. one engageable by said pin, located in the cam slot. a second arm pivotally connected to the fixed plate and on the same pivot as the first-mentioned arm. and having a portion that registers with the index graduations of the ilxed table, a stop bar on the second arm with which the other cam on the holder oi. the drill engages for moving the drill laterally, means for rotating the drill holder in its sleeve. the construction and arrangement being such that the included point angle at which the drill will be ground is determined and the angular relation of the axis or the drill is controlled which produces the relief angle, as described.

CARROLL B. ADAMS. 

